Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!tut.cis.ohio-state.edu!ucbvax!decwrl!decvax!ima!cfisun!lakart!dg
From: dg@lakart.UUCP (David Goodenough)
Newsgroups: comp.lang.c
Subject: Re: Addition of pointers
Message-ID: <542@lakart.UUCP>
Date: 9 May 89 14:09:35 GMT
References: <2299@mit-caf.MIT.EDU>
Organization: Lakart Corporation, Newton, MA
Lines: 32

From article <2299@mit-caf.MIT.EDU>, by vlcek@mit-caf.MIT.EDU (Jim Vlcek):
> In article <4093@ficc.uu.net> peter@ficc.uu.net (Peter da Silva) writes:
>>In article <563@lzaz.ATT.COM>, hutch@lzaz.ATT.COM (R.HUTCHISON) writes:
>>> 	midpoint_pointer = (start_pointer + end_pointer) / 2;
>>
>>You're right. It's a valid operation.
> 
> In what sense?  It's invalid C, that's for sure.
> 
> All you people who want to be able to add pointers, consider this:
> What is the significance of the sum of ``the location of Boston'' and
> ``the location of Detroit?''  Answer: none.

Taking this to it's (logical??????) conclusion, is not the point half way
between Boston and Detroit (say Elmira in Upstate NY :-) ) best defined
as:

Start at Boston, and go 1/2 way to Detroit, or in pointer arithmetic:

 	midpoint_pointer = start_pointer + (end_pointer - start_pointer) / 2;

Now, in scalar maths this is the same as the formula above, but pointers
are _NOT_ scalars: adjusting the formula again:

	midpoint_pointer = start_pointer / 2 + end_pointer / 2;

Now, just what the hell is half a pointer???????
-- 
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